1. Field of the Invention
The present invention relates to a method of growth of a single-crystal region of a III-V compound on a single-crystal silicon substrate. The present invention also relates to the device obtained by the present method. The present invention especially applies to the forming of a single-crystal region of a binary compound of gallium arsenide (AsGa) on a single-crystal silicon substrate on which are formed other semiconductor components.
2. Discussion of the Related Art
III-V compounds are currently used to form optoelectronic devices, for example, solar cells, lasers or diodes, or to form fast circuits.
It is known to grow, by epitaxy, a layer of a binary AsGa compound on a solid germanium substrate, germanium and AsGa having a similar mesh parameter. However, when AsGa is grown on an oriented single-crystal germanium substrate, the orientation of which is for example (100), the obtained AsGa layer exhibits a polycrystalline structure. Indeed, AsGa is a binary compound which may start its growth on an As plane or on a Ga plane. On the (100) oriented germanium surface, the AsGa nucleation may start from any point of the surface according to an As plane or to a Ga plane. AsGa grains, which have started, some from a Ga surface, the others from an As surface, tend to grow and form, when they join, grain joints. Such grain joints are called antiphase domains (APD) and correspond to defective regions which are undesirable when optoelectronic devices or fast circuits are desired to be formed in the AsGa layer.
To avoid forming of grain joints, the surface of the solid single-crystal germanium is generally altered to form steps on the edges of which, with adapted deposition conditions, it is possible to have the AsGa nucleation start preferentially from the same initial As or Ga plane. Optimally, the solid germanium surface is mechanically worked, for example, by polishing, to obtain a surface inclined by approximately 6° with respect to the (100) growth planes.
There currently is a need for III-V compound single-crystal regions, in particular of AsGa, on a silicon wafer to integrate optoelectronic devices or fast circuits formed at the level of the AsGa regions with the other semiconductor components formed on the wafer.
For this purpose, portions of a single-crystal AsGa layer previously formed on solid germanium are currently placed on the silicon wafer.
Indeed, even if it is known to directly grow a single-crystal germanium layer of a few micrometers on a single-crystal silicon wafer, the obtained single-crystal germanium keeps the crystalline information provided by the single-crystal silicon and is thus oriented, most often according to orientation (100) which corresponds to the usual orientation of silicon wafers used in microelectronics. For the same reasons as those discussed previously, if a III-V compound is grown by epitaxy on the germanium surface formed on the silicon wafer, the obtained structure is polycrystalline. Now, no simple means are currently known to mechanically work a germanium layer of a few micrometers and form surfaces inclined by 6° on which a single crystal of the III-V compound could grow.
Further, when germanium is grown on a “de-oriented” single-crystal silicon wafer, that is, the surface of which would have been polished according to a plane inclined with respect to the silicon growth planes, it can be observed that the germanium tends to return to a conventional orientation, and not to keep the de-oriented character of silicon.